1. Field of the Invention
The present invention relates to a digital protection and control device to which a digital sensor unit detecting AC electricity quantities of substation main equipment and outputting the detected quantities in digital values and a component control device controlling the substation main equipment are coupled via a transmission medium.
2. Description of the Related Art
A conventional protection and control system in a substation is shown in FIG. 1. In accordance with the recent development of communication and digital technology, some of protection and control systems in substations also use devices to which digital arithmetic processors and transmission mediums are applied.
In FIG. 1, Z1 shown by a frame depicted with a dot-dash line is a main control building of a substation. In the main control building Z1, a remote controlling equipment Z2 that relays information to/from a remote control station, a collective controlling-and-monitoring equipment Z3 that performs supervisory control of the entire substation, and main-circuit control devices Z5-1 to Z5-n installed for respective main-circuits such as power-transmission lines are coupled by a station bus Z7 (a serial transmission bus such as LAN). Further, protection devices Z6-1 to Z6-n to protect respective substation equipments Z8-1 to Z8-n, which will be described later, are connected to the main-circuit control devices Z5-1 to Z5-n respectively. Note that the remote controlling equipment Z2 and the collective controlling-and-monitoring equipment Z3 will collectively be referred to as a substation controlling-and-monitoring equipment Z4 for convenience sake.
The substation main equipments Z8-1 to Z8-n are connected to the main-circuit control devices Z5-1 to Z5-n and the protection devices Z6-1 to Z6-n via local control devices Z9-1 to Z9-n. The substation main equipment Z8-1, which is a kind of facility for power transmission lines, is constituted of a current instrument transformer Z10, a voltage instrument transformer Z11, a switchgear Z12 such as a circuit breaker or a disconnecting switch, a bus line Z13, and a power transmission line Z14.
The current instrument transformer Z10, the voltage instrument transformer Z11, the switchgear Z12, and the local control device Z9-1 are devices to which analog technology is applied. For connection between the substation main equipment Z8-1 and the local control device Z9-1, and between the local control device Z9-1 and the main-circuit control device Z5-1 or the protection device Z6-1, electric cables Z15 and Z16 appropriate for a volume of transmitted information are used.
Digital devices to each of which a digital arithmetic processor is applied are used as the remote controlling equipment Z2, the collective controlling-and-monitoring equipment Z3, the main-circuit control devices Z5-1 to Z5-n, and the protection devices Z6-1 to Z6-n. The station bus Z7 is used as a transmission medium for information transmission between the substation controlling-and-monitoring equipment Z4 (the remote controlling equipment Z2 and the collective controlling-and-monitoring equipment Z3) and the main-circuit control devices Z5-1. An electric cable Z17 appropriate for a volume of transmitted information is often used for connection between the main-circuit control device Z5-1 and the protection device Z6-1, a contact being an interface.
Each of the main-circuit control devices Z5-1 to Z5-n is constituted of an input converter unit, an input unit, an output unit, an analog input unit, an arithmetic unit, a communication unit, and a power supply unit. The input converter unit takes in an AC electricity quantity of a current or a voltage, and filters and A/D converts the analog input so that the analog input is converted to a voltage value or a current value on a level directly treatable in an electronic circuit. A contact input circuit is mounted on the input unit. A contact output circuit is mounted on the output unit. The analog input unit performs processing such as digital conversion of the AC electricity quantities. The arithmetic unit performs processing for realizing a control function. The communication unit performs transmission processing. The power supply unit supplies electricity to each of the units.
Likewise, each of the protection devices Z6-1 to Z6-n is also constituted of an input converter unit, an input unit, an output unit, an analog input unit, an arithmetic unit, a communication unit, and a power supply unit. The input converter unit takes in an AC electricity quantity of a current or a voltage and converts it to a voltage value or a current value on a level directly treatable in an electronic circuit. A contact input circuit is mounted on the input unit. A contact output circuit is mounted on the output unit. The analog input unit performs processing such as digital conversion of the AC electricity quantities. The arithmetic unit performs processing for realizing a protection function. The communication unit performs transmission processing. The power supply unit supplies electricity to each of the units.
A plurality of input units and a plurality of output units are mounted on each of the main-circuit control devices Z5-1 to Z5-n and the protection devices Z6-1 to Z6-n when necessary. Therefore, each of the main-circuit control devices Z5 and the protection devices Z6 has such a configuration that the units involved in input and output occupy most of each device.